A recent development in the food industry is the emphasis on intermediate-moisture foods which have the faculty of being stored and marketed in a substantially non-refrigerated condition. These foods were designed to avoid the need to be packaged in a hermetically sealed container and commercially sterilized or maintained in a frozen or refrigerated state throughout the period of distribution and storage by the consumer.
The intermediate-moisture foods are based on the principle of reducing the availability of water in the food for microbial growth. The availability for spore germination and microbial growth is closely related to its relative vapor pressure, commonly designated as water activity. It was found that the use of a wide variety of water-soluble solutes, or osmotic agents, has the effect of depressing the water activity of the foods to levels at which most bacteria will not grow.
The water activity of a food is defined as the partial pressure of water in the food divided by the saturation pressure of water at the temperature of the food. The water activity can be determined by placing a sample in a container which is then sealed, and after equilibrium is reached, determining the relative humidity above the sample. Most products of this type have between 10 to 40% moisture, and a water activity between 0.65 and 0.9.
An early application of the technique of controlling water activity was for animal foods. For example, U.S. Pat. No. 3,202,514, issued Aug. 24, 1965, discloses an animal food having 15 to 30% moisture and 15 to 35% water-soluble solids, principally sugar, with a proteinaceous meaty substance. Subsequently, other foods were formulated with an intermediate-moisture content, such as egg products (U.S. Pat. No. 3,640,731, issued Feb. 8, 1972), pancake batter (U.S. Pat. No. 3,753,734, issued Aug. 21, 1973) and whippable bases for confectionary use (U.S. Pat. No. 3,958,033, issued May 18, 1976). The water content and water activity of these foods are brought to as low a value as practical to insure their long-term stability without refrigeration. The main difficulty with these foods is that their low-moisture content may detract from their palatability, texture and mouth-feel. This technique therefore has found its greatest commercial applicability in the pet-food market where palatability requirements are not as stringent.
It is of course desirable to be able to avoid refrigeration and freezing of food products to reduce the cost involved, and particularly for the consumer, to avoid the inconvenience of unpacking, handling, and then defrosting the typically rock-hard frozen foods. However, freezing is an extremely safe and suitable technique for long-term storage and provides the manufacturer with great leeway in incorporating any of a wide variety of ingredients in foods which would otherwise be short-lived.
Accordingly, a class of intermediate-moisture foods has been found in accordance with application Ser. No. 763,613, filed Jan. 28, 1977, and application Ser. No. 871,995, filed Jan. 24, 1978, which combines the convenience of the freezing method of storage sought by manufacturers with the ease of handling desired by consumers. Such foods are normally stored at freezer temperatures, but upon removal from the freezer can be more readily handled because they retain a flexible consistency, are non-crystalline and spoonable within about 5 to about 15 minutes, and can be left at room temperature for an extended period of time as they possess the requisite microbiological stability.
The foods of the invention are generally characterized by a high sugar content, usually at least equal in weight to the amount of water present, in order to provide microbiological stability. The sugars employed have a low molecular weight, being primarily dextrose and fructrose, which comprise together at least about 50% and preferably at least about 75% of the total sugar content. Sucrose has a sweetness between that of fructose and dextrose. The fructose, which is sweeter than the dextrose, is preferred since it has a lesser tendency to crystallize and cause apparent hardness. For most foods, particularly where the food comprises an emulsion, it is preferred that the fats used, if any, include partially unsaturated fats which tend to provide superior flow properties and nutritional advantages, although less stable than saturated fats. The fat content is usually less than the water content in order to form a stable oil-in-water emulsion; the water content is preferably at least about 25% greater than the fat content.
The use of bacteriostatically effective amounts of sugar, however, imparts excessive sweetness to the ultimate food product. The problem of excessive sweetness has arisen previously in conjunction with the development of artificial sweeteners, and certain bitterness principles have been incorporated in such products to mask the undesirable taste. It was disclosed in U.S. Pat. No. 3,934,047, issued Jan. 20, 1976, that addition of aluminum potassium sulfate, naringen or a combination thereof to artificial sweeteners such as the saccharines or the cyclamates, or to higher caloric sweeteners such as sucrose, effectively reduced the perceived sweetness and bitter after taste of the artificial sweetener. It was postulated that the bitterness agent reduces the duration of sweetness, and presumably alters the manner in which sweetness is perceived.
In connection with neutralizing the bitter after taste of saccharine or saccharine salts, it was disclosed in German Pat. No. 2,060,634, issued Dec. 9, 1970, that the addition of about from 0.2 to 2.0 by weight percent of one or more substances having a bitter taste results in masking of the lingering bitterness associated with saccharine. Quinine sulfate and magnesium sulfate are specifically recommended as additives for use in this regard.
Such bitterness principles as quinine, theobromine and caffeine have also been advanced for use as flavor factors in synthetic and natural chocolate compounds and chocolate-flavored beverages to impart a bitter taste to the resultant foodstuff. U.S. Pat. Nos. 2,835,592, issued May 20, 1958, and 3,102,815, issued Sept. 3, 1963, are illustrative of such disclosures.
Further flavor modifiers which impart a bitterness to the compounds in which they are incorporated are disclosed in U.S. Pat. No. 3,647,482, issued Mar. 7, 1972, to Yueh, and U.S. Pat. No. 4,006,261, issued Feb. 1, 1977, to Pickenhagen et al. Yueh's patent discloses the use of ribonucleotides, ribonucleosides and their deoxy analogues to reduce or eliminate the bitter after taste associated with saccharine or saccharine salts, or compositions containing these sweeteners. Pickenhagen et al. disclose the use of compositions of theobromine in combination with cyclic dipeptides to impart bitterness and astringency properties to various foodstuffs, especially cocoa products, animal foods, beverages, pharmaceutical preparations and tobacco products.
In U.S. Pat. No. 3,371,543, issued Feb. 13, 1973, the use of theobromine, caffeine or naringen to impart bitterness to nitrogen-based flavor intensifiers is disclosed.
It is an object of the present invention to provide a class of foods which are normally maintained at freezer temperature, but which possess the requisite microbiological stability for storage at refrigerator or room temperatures for an extended length of time without spoilage.
It is another object of the present invention to provide an improved bacteriostatic intermediate moisture food product which is ready for use at freezer temperature, the perceived sweetness of which has been reduced through the addition of a bitterness factor.
It is a further object of this invention to accomplish the above-specified reduction in sweetness perception through the use of certain quinine salts.
Other objects, and advantages, of this invention will be apparent from the ensuing specification and examples.